@SadaoTurner posted
this image of Olympics wi-fi police, who seek unauthorized wi-fi signals
and shut them down. Why go through all that trouble? Because Olympic partner
BT runs some 1,500 paid hotspots at the event. Via The
Verge

There's only 13 legal channels for use in England; since there is overlap of the high and low frequencies of each channel, you can really only have three interference-free hotspots in a given area, so the engineers have doubtless gone to great lengths to place the APs on specific channels distinct for each location to give the best chance of interference-free use for all.

That they chose to charge money for use of the infrastructure is an orthogonal decision -- but having guys with tools to find "rogue" transmitters is a simple matter of politeness. Without those guys, it probably wouldn't work well for anyone, rogue or paying user.

Also, with the number of wireless signals that are not wi-fi (wireless tv cameras, walkie-talkies, microphones, emergency dispatch, etc.), it would be very easy for a signal in an unauthorized bandwidth to take down something critical.